The present invention relates to the continuous casting of molten metal onto the surface of a chilled metal surface which is rotated to produce rapidly solidified strand. The cast strand may be crystalline or amorphous and the strand produced may be a narrow ribbon, wire or strip of various widths. The solidified strand exits from a rotating surface which could be a water cooled wheel, drum or belt. To insure the strip exits the substrate at a specific location to permit coiling, various means to separate the strip from the substrate have been used.
It is generally known to use mechanical means referred to as stripper bars to assist in the separation between the molten metal and the rotating chilled surface. U.S. Pat. No. 4,644,999 shows a device 22 which directs the strip off a casting wheel and to a coil winder. The separation means also provides direction for the strip to the coiler.
Another example of a mechanical scraper or knife is shown as 18 in U.S. Pat. No. 4,789,022 which serves to separate the metal strip from the solidification support.
Wedge-shaped blocks have scraped strip from a wheel for a long time as demonstrated by U.S. Pat. No. 2,847,737 which has a stripper shoe 14 for this function.
U.S. Pat. No. 4,770,227 uses a similar wedge-shaped releasing member 7.
U.S. Pat. No. 4,301,854 lists several solutions to stripping cast strip from the inner surface of a chill roll. Included were the use of fluid jets, scraper blades, brushes, magnetic devices and suction means to lift the filament from the chill roll.
The prior work of most interest to the present invention is the use of gas or fluids to cause the separation of the cast strip from the rotating substrate surface. An example of patented work in this area is U.S. Pat. No. 4,301,855 which uses a nozzle 7 to blow a gaseous medium tangentially to the roll surface in a direction opposite the rotation of the roll. The nozzle is positioned to be at a circumferential location on the roll where the molten metal is solidified.
In U.S. Pat. No. 4,776,383 a stripper nozzle 90 is used to detach the strip from the drum and may use air or protective gas as the fluid.
Japanese patent publication No. J59232653 blows a gas to peel the cast strip from the roll.
U.S. Pat. No. 4,221,257 blows inert gas in the direction of substrate rotation ahead of the molten pool to improve the casting conditions but is not intended for the removal of strip from the substrate.
The previously mentioned references have attempted to improve the separation of the cast strip from a rotating surface through several means which have not been entirely successful. If the adhesion of the strip is not broken prior to a complete revolution of the wheel, a catastrophic failure condition occurs.
The prior attempts to use fluid separation means have not provided a high pressure gas nozzle which may be closely positioned to the rotating substrate. Close positioning of the nozzle has a high risk for damage from the strip which is rotating around the substrate. Any strip build-up on the substrate may contact the nozzle if positioned too close. There is a considerable need for a system which can be used to remove cast strip from the substrate safely.